Telephone-transformer



V. L. SMITH. TELEPHONE TRANSFORMER.

APPLICATION FILED MAB. x. 1911.

Patented May 11, 1920.

M wnfor: V/rqi/ L. Smifh.

STATES mm L. smell, or CHICAGO. ILLINOIS, sssronon. r msmm PATENT OFFICE.

INCORPORATED, OF NEW YORK, N. Y., A CORIORATION OF NEW YORK.

TELEPHONE-TRANSFORMER to re use to a minimum the citizen of the" United Chicago, in the county of Illinois, have invented. certain new and Bit' known'that I 'Vmom L. SMITH, :1

States, residin of (look and btnte useful Improvements in Telephone-Transis a full, clear, concise, and exact description. Thisinvention relates to telephone transformers, and-is particularly useful in 'connection with phantom repeating coils, -duplex' auto-transformers and similar transformers used in telephone circuits.

In such devices it is essential, in order to reduce to a minimum the injurious characteristic'known as cross-talk," that the socalled phantom windings be as closely balanced as possible with reference to their ohmic resistance, capacity and indm-tance; or, in other Words said windings must he as nearly as possible in ohmic, electrostatic and electromagneticbalance. It is not :1, diffi- 'cult matter to balance the phantom windin'gs us to their ohmic resistance, as is Well understood by those skilled in this art. In

spite, however, of the greatest care in manufacture,'tlie phantom windings may he unbalanced electrostatically and electromagneticslly acteristi'cslhappen to equalize one another, the transformer may be unfit for use by reason of-the ci'oss-talk which it would intro duce into the circuit.

The general object of the invention is to provide in a. device of the kind mentioned, means for assisting in the satisfactory halancin of the phantom windings. in order injurious char acteristic known-as crosstalk.

In general, the invention is characterized by a supplementary Winding or coil connected inseries with one of the phantom windings and arranged in mutually inductire relation to the windings of the trans former. This supplementary winding has substantially no effect upon the electrostatic Specification of Letters Patent.

, and unless thes,e unhalanccd char- Patented May 11., 1926.

Application filed Karen 1, 1917. Serial No. 151,722.

The invention will be understoodf fro m mimcrmc GOMPAKY,

the following description tukenin connection with the accompanying drawing, in which Figure 1 is a perspective view of a phantom repeating coil having one form of the invention embodiedtherein, and Fig. 2 iso similar view showin another 'form in which the invention may e embodied.

Figs. 1 and 2 show phantom coils in the condition in which they iu'e tested before being potted. A tape-wound coil is shown at 3, ends 4, 5, 6 and 7 and the ends 8, 9, 10 and l1 of the non-phantom windings. Such repeating" coils before potting are tested for cross-talk in any suitable well-known manner, as by an arrangement of artificial lines. If, in testing such a coil. it is found that the phantom windings are so much unbalanced that anobjectionable amount of cross-talk results, the phantom windings are first balanced in any well-known man neras to ohmic resistance: If the amount' of cross-talk is still objectionably large, it can be further reduced by the employment of the characteristic fea ture of the present invention, which willnow -be described. 4

invention may be embodied. The loose end of the wire 7, which is one of the terminals of the phantom windings. is shown extended along and partially looped around the tape-wound coil 3, and is secured by a hand of tape 13 in the manner shown. The effect of this partial looping of the wire 7 around the coil is to vary the inductance'of from which project the of the phantom-windiugs 1 Y .t i repeatmg F 1g. 1 shows a simple form' 'in which i the Winding 6-7, and thus the electromagnotic balance between the phantom win ings -L-5 imd 67. looped end of the wire 7 which will most nearly cause perfect balancing of thephantom v ndin s and therefore give the least cross-talk in 1e circuits of the repeating coil, (an easily be determined by moving the end of the wire 7 todifferent positions around the coil 3. \Vhcn the most advantageous position is found. the looped end is secured in that position by the tape 13 or in any other suitable manner. The repeating coil can then be potted in the 'usual manner.

Fig. 2 shows a form of the invention which operates upon the same principle as the form shown in Fig. 1 but provides for The position of the fect balanci" 1n any position on ,the outside of the coil 3, where they will link with the leakage flux and introduce impedance into-the circuit of the hantom L-It can easily be eterminedb'y, experiment which side of the supplementary winding 14 should lie a inst 0011- 3, and also what the position 0 the supplementary winding 14 should be in orderto obtain the most perfect balance. It is a simple matter for the tester to make a few turns in either the wire 4 or the' wire-7 and theiix move these turns around on the surface of the coil 3 until the cross talk, due tothe unbalanced condition of the phantom windings 45 and 6-7, has de creased to the minimum value which it seems possibleto obtain. When this position for" the supplementary winding 14 has been found, said winding can be secured in that location in any suitable manner as by a tap'elfi'extending around the coil 3.

In the appended claims the expression supplementary winding is used to denote both the looped end of the wire 7 shownin Fig. 1 and such an arrangement as that 1n dicated by the winding 14 in Fig. 2, and

Y all other equivalent arrangements, e.. those whose function it is to supplement the action of one or more of the main windings of the coil and thereby" to remove a lackof balance betweenthe main windings and whose action is thereforebsubsidiary to the action of the main windings. Y What is 'claimedjs 1. In a telephone transformer, a plurality of transformer windings, and a supplementary winding connected in series with one of said transformer windings and arranged to link 'with the leakage flux from said trans former windin 2. ,,In a telepfifme transformer, a plurality windings.

, and a supplemenof transformer windin n series with one tary winding connecte of said transformer win dings and arranged 60 to link only with the leakage flux from said ings and a supfle'mentary coil arranged extoroid and adapted to link flux from said transformer teriorl of sex with t eleaka 4. In a telephone transformer, a "lurality ofwindings, a supplementary winding connected in series with one of said transformer windings,'and.means for securing said supplementary winding in mutually inductive relation to said transformer windings at a the induetivdeflect of said supplementary winding will most nearly.elfect rfect electrostatic' and electroma etic, ha ance of the windings of said trans ormer.

5. In a phantom ity of repeating wi lngs, including phantom windings, and means for assisting in the balancing of the phantom repeatin windings comprising a supplementary wind lng counecte phantom windings and arranged to link with the leakage flux from the windings of the repeating coil. I

6. A method of.lbalancing the windings int determined by trial where re eating coil, a pluralin series with one of said of a telephone transformer which consists in providing one of the ends of one of the transformer windings with a sup lementary winding, determining by trial t e position relative to the transformer where the inductive efi'ect on the transformer windings VIRGIL L. SMITH, 

